package com.rural.bus.utils;

public class DistanceUtil {
	static double DEF_PI = 3.14159265359; // PI
	static double DEF_2PI= 6.28318530712; // 2*PI
	static double DEF_PI180= 0.01745329252; // PI/180.0
	static double DEF_R =6370693.5; // radius of earth
	
	public static double GetShortDistance(double lon1, double lat1, double lon2, double lat2)
		{
			double ew1, ns1, ew2, ns2;
			double dx, dy, dew;
			double distance;
			// 角度转换为弧度
			ew1 = lon1 * DEF_PI180;
			ns1 = lat1 * DEF_PI180;
			ew2 = lon2 * DEF_PI180;
			ns2 = lat2 * DEF_PI180;
			// 经度差
			dew = ew1 - ew2;
			// 若跨东经和西经180 度，进行调整
			if (dew > DEF_PI)
		dew = DEF_2PI - dew;
			else if (dew < -DEF_PI)
			dew = DEF_2PI + dew;
			dx = DEF_R * Math.cos(ns1) * dew; // 东西方向长度(在纬度圈上的投影长度)
			dy = DEF_R * (ns1 - ns2); // 南北方向长度(在经度圈上的投影长度)
			// 勾股定理求斜边长
			distance = Math.sqrt(dx * dx + dy * dy);
			return distance;
		}

}
